I nursed my daughter for two years. That's not for a pat on the back, or for you to think it's creepy, or anything in between - it's just to say that I'm pretty well-versed on the subject of boob juice and the storage thereof.
Due to the shape of my daughter's mouth, we had to almost exclusively pump for the first four months or so until her mouth grew. So we really had to get a pumping/freezing/refrigeration system down pretty early. Which was awesome every 3 hours all night long, all day long, through work, etc., etc., etc.
At first we tried Medela bags (LINK), because I used a Medela Pump-In-Style Advance pump (which I loved, and think they have great products). The bags were great - they had little sticky things that attached to the pump so that you could pump straight into them rather than using a bottle as a middleman. The bottom is also shaped like this:
This is not a vagina, it's the bottom of the bag that is shaped so that it can stand up. This is pretty nice if you need to dump milk into it from a bottle, it can stand on its own while you open the lid, etc., etc. And plus, I guess if you're into things vaguely resembling vaginas, it also has that benefit.
The downside is the cost. Let's say you only pump three times a day at work or whatever that you need to refrigerate. (For me this ended up being quite a bit more.) The link I provided above shows that 50 bags are $17.09. That's certainly not breaking the bank, but how many bottles do you get out of $18/worth of formula? I validly don't know, and I'm sure it depends on the formula, but it makes breastfeeding less cost-effective.
So, I gave the Up & Up from Target a try next (LINK). $7.99 for 50. I won't get into a long spiel, they leaked, I didn't get more.
I really liked the Lansinoh lanolin and stuff, so I figured I'd give those a try next (LINK). $9.99 for 50 of them. So, not too much more than the Up & Up, but still significantly less than the Medela ones.
These ones worked great. They didn't have the little pieces of sticky tape on it to attach to the pump, but you could rectify that by just taping it on. The bottom didn't have that appealing standing-up-vagina shape, it is just shaped like an envelope at the bottom, but I was pretty well a pro with the pump bottles by this place and it didn't cause any issues. No leaking, they can be made to lie flat in the fridge or freezer so they store easily, all around good choice to hold that liquid gold.
We mostly did baby-led weaning, but did have to make some of our own baby food and add iron-enriched oatmeal when our daughter was anemic around 9 to 11 months. I didn't think of it at the time, but these would have probably been pretty good to hold that homemade baby food. (Edit to add - I just googled this to make sure I'm not off-base, and it sounds like that's a legitimate use of these.)
So, all in all, if you're looking for a way to efficiently store your breastmilk in a way that won't ooze it out all over the fridge at work, and also won't cost a ridiculous amount of money for what essentially is a small Ziploc bag, I'd strongly recommend the Lansinoh bags. Plus, if you also use their breast pads (which I did for very similar reasons as this whole saga), they usually put a couple of spare storage bags and some coupons in the top of the breast pads box.
Since I probably can't say "breast" a whole ton more, I'll leave it at that.
Value: $9.99 for 50. The best for the money that I can find, 10/10.
Child entertainment level: 0/10, but kids aren't really the crowd. Maybe they could make one a hat?
Practicality: Again, just had the best combination of all factors that I could find. 10/10